Red, green and blue Light-Emitting Diodes (LEDs), which may realize very bright white light, have been developed based on the development of, for example, a gallium nitride (GaN) metal organic chemical vapor deposition method and a molecular beam growth method.
These LEDs substitute for conventional light sources because they include no environmentally noxious materials, such as mercury (Hg), which are used in conventional lighting appliances, such as, for example, incandescent lamps and fluorescent lamps, thus being very environmentally friendly, and also have several advantages, such as, for example, a long lifespan and low power consumption. The salient competitiveness of the LEDs is to realize high brightness through high-efficiency and high-output chip and packaging technologies.
FIG. 1 is a schematic sectional view of a conventional light-emitting device package, which includes a package body 10, an adhesive layer 20, and an LED 30.
Referring to FIG. 1, when the LED 30 is formed via stamping after the adhesive layer 20, which is in paste form, is formed on the package body 10, the adhesive layer 20 is disposed between the LED 30 and the package body 10, thereby causing the two 30 and 10 to be coupled to each other.
FIGS. 2a to 2c are different plan views of the light-emitting device package illustrated in FIG. 1.
When stamping the LED 30, the adhesive layer 20 is in the form of a paste, thus showing various plan shapes depending on the viscosity thereof. In the normal case, the plan shape of the adhesive layer 20 around the LED 30 is as illustrated in FIG. 2a. However, the adhesive layer 20 may widely spread in the radial direction around the LED 30, as illustrated in FIG. 2b. Alternatively, the adhesive layer 20 may widely spread in only a direction around the LED 30. As described above, when the LED 30 is bonded to the package body 10 via stamping, it may be difficult to minimize or control the spreading of the paste-type adhesive layer 20.
In the case where the paste-type adhesive layer 20 spreads abnormally widely, as illustrated in FIG. 2b or 2c, the adhesive layer 20 may be discolored by deep ultraviolet light, which is emitted from the LED 30 and is in a wavelength band within a range from 270 nm to 285 nm. At this time, the discolored adhesive layer 20 may absorb a great quantity of light, thus suffering from low light emission efficiency and poor heat dissipation. In particular, when the discolored adhesive layer 20 is subsequently decomposed, micro cracks, etc. may form, which may reduce the lifespan of the light-emitting device package by allowing moisture to permeate therein.